An adjoint method for the calculation of remote sensitivities in supersonic flow

This paper presents an adjoint method for the calculation of remote sensitivities in supersonic flow. The goal is to develop a set of discrete adjoint equations and their corresponding boundary conditions in order to quantify the influence of geometry modifications on the pressure distribution at an arbitrary location within the domain of interest. First, this paper presents the complete formulation and discretization of the discrete adjoint equations. The special treatment of the adjoint boundary condition to obtain remote sensitivities or sensitivities of pressure distributions at points remotely located from the wing surface are discussed. Secondly, we present results that demonstrate the application of the theory to a three-dimensional remote inverse design problem using a low sweep biconvex wing and a highly swept blunt leading edge wing. Lastly, we present results that establish the added benefit of using an objective function that contains the sum of the remote inverse and drag minimization cost functions.     

EXPERIMENTAL STUDY AND NUMERICAL SIMULATION OF MECHANICAL BEHAVIOR OF TRUSS BOOM DURING HOISTING PROCESS

吊机是海洋钻井平台的关键设备,为确保整套系统的安全运行,研究桁架式吊臂在变幅平面内的结构力学性能. 考虑到桁架式吊臂的结构特点及构件性能退化等不确定因素,采用有限元方法,以承载杆件应力为修正指标考虑损伤的影响,建立了吊臂的三维数值模型,对变幅全过程进行了数值模拟和试验研究,结果表明：应用该方法可以比较真实地模拟出吊臂的变幅过程和结构力学性态,确定结构的薄弱部位,为吊装作业和吊臂结构的安全运行提供有价值的建议,适合工程应用.     

Numerical simulations for gas-structure interaction in inflated deployment of folded membrane boom

It is very important for gas-structure interaction between compressible ideal gas and elastic structure of space folded membrane booms during the inflatable deployment. In order to study this gas-structure interaction problem, Arbitrary Lagrangian-Eulerian (ALE) finite element method was employed. Gas-structure interaction equation was built based on equilibrium integration relationship, and solved by operator split method. In addition, numerical analysis of V-shape folded membrane booms inflated by gas was given, the variation of inner pressure as well as deployment velocities of inflatable boom at different stage were simulated. Moreover, these results are consistent with the experiment of the same boom, which shows that both ALE method and operator split method are feasible and reliable methods to study gas-structure interaction problem.     

对二次曲面教学中伸缩法的探讨

Mathematica软件具有强大的绘图、程序设计功能,在高等数学教学中引入Mathematica软件作为辅助工具,利用软件的绘图和程序设计功能,直观描述二次曲面伸缩形变的动态过程,有利于增强教学内容的直观性,帮助学生掌握所学知识,提高学生分析问题和解决问题的能力．     

一种双作用多级液压缸的设计与应用

通过对一种双作用多级液压缸伸缩过程的分析,弄清了影响此种双作用多级液压缸动作顺序的几何要素和系统的力学要素,确定了此种双作用多级液压缸设计原则及液压缸正常工作的条件,为此种双作用多级液压缸的设计及应用提供了理论依据.     

截面型式对伸缩臂局部稳定性的影响

对四边形、六边形截面伸缩臂的稳定性计算方法进行了探讨.编制了相应的计算程序,以QY50汽车起重机为例,对不同截面形式五节伸缩臂稳定性进行了计算,并进行了对比分析.     

挖掘机动臂重量及重心位置的计算方法

提出了挖掘机动臂重量及重心位置的新的计算方法,结果精确可靠,该方法也适合于计算其它复杂的空间封闭箱型结构的有关机械力学特征。     

Modeling and Dynamic Analysis of Telescopic Systems of Structural Members with Clearance

The dynamic behavior of multi-section constructions with clearance during extending and retracting motion of the sections is analyzed. First, an appropriate physical modeling is introduced before next, the governing boundary value problem is derived by applying Hamilton's principle. Then, a classical discretization procedure is used to generate a coupled system of nonlinear ordinary differential equations as the corresponding truncated mathematical model. Performing appropriate simulations to be verified by results of an alternative software package and partly validated by some preliminary experiments, the vibrational behavior of the suggested type of multi-section telescoping systems can be studied in detail.     

Weakly nonlinear propagation of small-wavelength,impulsive acoustic waves in a general atmosphere

Multiple-scale asymptotic analysis is applied to small-wavelength, weakly nonlinear propagation of an impulsive acoustic wave in a general (3D, in-motion and time dependent) atmosphere. In keeping with previous work on sonic booms and nonlinear acoustics in general, the result is a combination of ray tracing and a generalised Burgers equation describing evolution of the waveform carried by a ray. This is nonetheless, to our knowledge, the first derivation of such a model based on asymptotic analysis of the governing equations for a general atmosphere. Results are given, discussed and compared with measurements for the particular example of the test explosion known as Misty Picture.     

CFRP薄壁管空间伸展臂模态与影响参数分析及试验

通过单向拉伸测试和理论计算得到4层(45°/-45°/45°/-45°)铺设碳纤维增强复合材料(CFRP)的弹性模量,作为数值分析的材料参数.由激光测振系统测试了CFRP薄壁管空间伸展臂自振模态,得到自振频率和振型.利用ABAQUS建立了CFRP薄壁管空间伸展臂自振模态有限元模型,分别采用分层和整体材料参数分析了自振模态,得到的自振频率和振型与试验结果吻合较好,进而计算分析得到CFRP薄壁管空间伸展臂线刚度(EI/L)和刚度线密度比(EI/m)对频率的影响关系.研究结果对CFRP薄壁管空间伸展臂设计和深入研究具有重要参考价值.